I just looked under the hood of my car and my valve cover was filthy!! Is this normal? I live in So California so not exceptionally dusty here. Anyone else's experience similar?

 

Normal. I live in Phoenix, the dust bowl of the SWest......and.........mine was dirty a week after I bought the car.
I stopped "washing" engines a long time ago. Created more problems than it was worth. I think just wiping these things off with some cleaner and a towel is about all you need to do to make it look a lot better.

 

It is normal. It is also a lot easier to keep clean than it is to clean it. Next time you detail start with the engine the afterwards wipe with damp soapy cloth at each carwash. Mine is in pristine condition such that the dealer wiped it down before closing the hood.